Conventional automatic drip coffee makers utilize a removable filter basket and paper filter to hold the coffee grounds while coffee is brewed. The filter basket is usually supported by a flange which engages with tracks in the coffee maker. The paper filter is disposed inside the filter basket, and the coffee grounds are placed on top of the filter. Water from the coffee maker is poured over the coffee grounds and passes through the paper filter. The hot water then flows through a small opening in the bottom of the filter basket into a coffee pot or other container disposed beneath the basket.
One problem which has been encountered with automatic drip coffee makers is that the paper filter tends to collapse so that a portion of the water flows over the top of the filter rather than through the filter. When the walls of the filter collapse, coffee grounds may be washed over the filter and into the pot of coffee being made.
In an effort to prevent the paper filter from collapsing during use, the walls of the filter are usually pleated. The pleats in the side walls of the filter provide some strength and rigidity. However, despite the presence of pleated side walls, there is still a problem with the side walls of the filter collapsing during use. Accordingly, there is a need for some type of filter support to prevent the side walls of the filter from collapsing during use.
Attempts have been made in the past to provide means for holding the side walls of the filter in an upright position. Several manufacturers of coffee makers have provided clips on the top edge of the filter basket to engage the edge of the filter and hold it in place during use. Another approach which has been tried is to use a radially expandable ring which fits into a circumferential groove in the filter basket. The top edge of the filter paper is pressed into the circumferential groove and held there by the expandable ring. Such devices add to the cost of the coffee maker and are not widely used.
Other devices used to support disposable coffee filters are disclosed in the patents to Benedict, U.S. Pat. No. 4,735,719; Sandvig, U.S. Pat. No. 4,728,425; McMichael, U.S. Pat. No. 4,865,737; and Johnston, U.S. Pat. No. 4,963,262. The Benedict patent teaches a circular frusto-conical shaped plastic filter support which wedges itself in the filter basket. The patent to Sandvig discloses a similar frusto-conical shaped filter support, but which rests against the bottom of the filter basket. The patent to McMichael discloses a cylindrical, wire-mesh filter support having an open top and bottom which rests against the bottom of the filter basket. The patent to Johnston discloses a ring-like filter support having downwardly projecting legs which support the ring in a predetermined position within the filter basket.
These prior art devices share one or more of the following disadvantages. Some of the prior art filter supports tend to flatten the pleats in the side walls of the filter thereby interfering with the filtration process. Others have large surface areas on which the coffee grounds collect thereby preventing uniform distribution of the grounds. Moreover, most of the prior art devices are sized and shaped to fit the coffee basket of a particular type of coffee maker and are not useable in connection with different types. Accordingly, an improved filter support which overcomes these problems is needed.